Thanks to his Avengers: Age of Ultron co-star Robert Downey Jr., Chris Hemsworth accepted the ALS Ice Bucket Challenge, which raises awareness for Lou Gehrig's disease. "I didn't do it within 24 hours, so I'll donate some money as well, and everyone should get involved," he said Monday. After ice water was dumped over his head, the Australian actor said, "That's rather cold. It's a little bit refreshing actually."

Jimmy Kimmel, meanwhile,took time out of his "very important" fly fishing trip to accept the challenge from "former friend" Kerry Washington's and the "honorable" Mayor of Toronto Rob Ford. Instead of dumping ice over his head, though, Kimmel asked his cousin and his wife to dump it in his fishing wader.

Pulling down his pants, he clarified, "I'm wearing underwear, just in case you were wondering."

After his wader was stuffed with ice, Kimmel told wife Molly McNearney, "I think maybe put some water in there to loosen it and get it down to my genitals. There we go. Oh, my God...This is terrible!"

He then joked, "My nuts are the size of Raisinets...Take me to the hospital!"

Kimmel nominated his faux nemesis, "Matt Effin' Damon."

"Let's see you get out from behind the candelabra and get some ice down your pants, baby," he said.

Vanessa Hudgens squealed when she got doused, as did her nominee, Spring Breakers' Ashley Benson.

One Direction's Niall Horan did his ALS Ice Bucket Challenge in the shower—and in a white shirt, too!

Dwayne Johnson—aka The Rock—nominated Brad Slater, Channing Tatum and Mark Wahlberg. Allison Williams accepted Girls co-star Lena Dunham's challenge, making her the final lead actress from the HBO comedy to participate. "Every girl on Girls has had hard nipples in last 24 hours," Dunham tweeted.

Other participants included Lily Collins, Cindy Crawford, Grant Gustin, Jessica Szohr and Miles Teller. Several celebrities also donated $100 or more to fund amyotrophic lateral sclerosis research projects.